Crosslinkable elastomer composition and fluororubber molded article

ABSTRACT

A crosslinkable elastomer composition including a crosslinkable elastomer and a surface-oxidized non-oxide ceramic. Also disclosed is a fluoroelastomer molded article having a weight reduction percentage of 2.5% by mass or less and an amount of particles generated of 0.05% by mass or less after O 2  plasma irradiation, a weight reduction percentage of 1.8% by mass or less, an amount of particles generated of 0.05% by mass or less after NF 3  plasma irradiation, and a compression set of 50% or less after aging at 300° C. for 70 hours.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2018/038627 filed Oct. 17, 2018, claiming priority based onJapanese Patent Application No. 2017-201923 filed Oct. 18, 2017.

TECHNICAL FIELD

The invention relates to crosslinkable elastomer compositions andfluoroelastomer molded articles.

BACKGROUND ART

Members used in semiconductor manufacturing devices, such as CVDapparatuses and erchers, are required to have resistance to NF₃ plasmatreatment and O₂ treatment that are performed in the production process.An example of known compositions constituting such a member is acomposition containing a crosslinkable fluorine-containing elastomer andSiO₂ as disclosed in Patent Literature 1. Another example thereof is acomposition containing a crosslinkable fluorine-containing elastomer andsilicon carbide particles having a bulk density of 0.15 g/cm³ or less asdisclosed in Patent Literature 2.

CITATION LIST Patent Literature

-   Patent Literature 1: WO 2005/17017-   Patent Literature 2: JP 2012-509975 T

SUMMARY OF INVENTION Technical Problem

The invention aims to provide a crosslinkable elastomer compositionhaving a small weight reduction percentage and amount of particlesgenerated after plasma irradiation under specific conditions and a smallcompression set at high temperature.

Solution to Problem

The inventors found through various studies that use of asurface-oxidized non-oxide ceramic filler can improve the weightreduction percentage and amount of particles generated after plasmairradiation under specific conditions and the compression set at hightemperature, completing the invention.

In other words, the invention relates to a crosslinkable elastomercomposition including a crosslinkable elastomer and a surface-oxidizednon-oxide ceramic filler.

The non-oxide ceramic filler is preferably silicon carbide.

The non-oxide ceramic filler preferably has an average particle size of0.1 μm or smaller.

The crosslinkable elastomer is preferably a copolymer oftetrafluoroethylene and perfluoro(alkyl vinyl ether).

The invention also relates to a fluoroelastomer molded article having aweight reduction percentage of 2.5% by mass or less and an amount ofparticles generated of 0.05% by mass or less after O₂ plasma irradiationunder the following conditions, a weight reduction percentage of 1.8% bymass or less and an amount of particles generated of 0.05% by mass orless after NF₃ plasma irradiation under the following conditions, and acompression set of 50% or less after aging at 300° C. for 70 hours, theconditions being:

Sample: O-ring (AS-568A-214)

Measurement Details:

(1) O₂ Plasma

Plasma irradiation device: ICP high-density plasma device (MODELRIE-101iPH available from Samco Inc.) Irradiation conditions

Gas flow rate: 16 SCCM

RF output: 400 Wh

Pressure: 2.66 Pa

Etching time: 30 minutes

Temperature: 100° C.

These conditions allowing a perfluoroelastomer (non-filler) to be etchedat a rate of 12000 Å/min

(2) NF₃ Plasma

Plasma irradiation device: ICP high-density plasma device (MODELRIE-101iPH available from Samco Inc.)

Irradiation Conditions

Gas flow rate: 16 SCCM

RF output: 400 Wh

Pressure: 10 Pa

Etching time: 4 hours

Temperature: 200° C.

These conditions allowing a thermally oxidized silicon (SiO₂) wafer filmto be etched at a rate of 90 Å/min.

Advantageous Effects of Invention

The crosslinkable elastomer composition of the invention, containing asurface-oxidized non-oxide ceramic filler, can simultaneously achieve asmall weight reduction percentage and amount of particles generatedafter plasma irradiation (plasma resistance) and a small compression setat high temperature (heat resistance).

DESCRIPTION OF EMBODIMENTS

The crosslinkable elastomer composition of the invention contains acrosslinkable elastomer and a surface-oxidized non-oxide ceramic filler.The filler may not be completely surface-oxidized and may be partiallysurface-oxidized. The surface-oxidation state can be determined byelectron spectroscopy for chemical analysis (ESCA). ESCA enableselemental analysis of a site about 3 to 5 nm deep from the surface of aparticle, and thus can determine whether the surface of the filler isoxidized or not.

Examples of the non-oxide ceramic filler include, but are not limitedto, a carbide, a silicide, a sulfide, and a fluoride. Examples of thecarbide include titanium carbide, boron carbide, zirconium carbide,hafnium carbide, tantalum carbide, tungsten carbide, niobium carbide,and silicon carbide. Examples of the silicide include titanium silicide,molybdenum silicide, and zirconium silicide. Examples of the sulfideinclude tungsten sulfide and molybdenum disulfide. Examples of thefluoride include aluminum fluoride, yttrium fluoride, and bariumfluoride. In order to simultaneously achieve a small weight reductionpercentage and amount of particles generated after plasma irradiation(plasma resistance) and a small compression set at high temperature(heat resistance), preferred among these is silicon carbide.

Hydrophobic silica, for example, can reduce the compression set butunfortunately increases the weight reduction percentage after NF₃ plasmairradiation, i.e., has insufficient plasma resistance. In contrast,silicon carbide without surface oxidation can reduce the weightreduction percentage and amount of particles generated after plasmairradiation but unfortunately increases the compression set at hightemperature, i.e., has insufficient heat resistance.

In the case of silicon carbide, for example, the surfaces thereof areoxidized into SiO₂. In ESCA measurement, a peak assigned to SiO₂ and apeak assigned to SiC are observed. The peak assigned to SiO₂ and thepeak assigned to SiC preferably give a ratio (SiO₂:SiC) of 1:9 to 9:1,more preferably 3:7 to 6:4. A peak ratio of less than 1:9 tends to causeinsufficient surface oxidation and fails to achieve a sufficient effectof improvement. A peak ratio of more than 9:1 tends to cause excessivesurface oxidation and fail to achieve a sufficient effect ofimprovement.

The non-oxide ceramic is preferably powdered by a pulverization using apulverizer such as a jet mill or by powder formation in which a nuclearis generated and grown from an atom or a molecule. In the latter case,methods are sorted into a gas phase method, a liquid phase method, and asolid phase method, according to the state of the starting material. Anymethod may be employed as long as the resulting powder of the non-oxideceramic has a sufficient purity. Among various non-oxide ceramics,silicon carbide preferably has a purity of 95% or higher in order toachieve excellent plasma resistance.

The non-oxide ceramic filler may be in any form, such as powder,particles, fibers, and whiskers. The non-oxide ceramic filler ispreferably in the form of particles in terms of processability andpreferably has an average particle size of 10 μm or smaller, morepreferably 0.1 μm or smaller. The non-oxide ceramic filler having anaverage particle size of greater than 10 μm may cause poor reinforcementand thus a greater amount of the non-oxide ceramic filler may need to beadded to a compound, impairing the characteristics of a resulting moldedarticle as a seal material. In the case of using the resulting moldedarticle as a seal material of a semiconductor device, the non-oxideceramic filler has an average particle size of 0.1 μm or smaller,preferably 0.01 to 0.1 μm, in order to reduce generation of particles.The lower limit of the average particle size is not limited.

The percentage of the non-oxide ceramic filler whose surfaces areoxidized to a depth of 2 nm or more is preferably, but not limited to,10 to 100% by mass, more preferably 30 to 100% by mass, in 100% by massof the non-oxide ceramic filler.

The non-oxide ceramic filler is present at any amount, preferably 1 to40 parts by mass, more preferably 5 to 25 parts by mass, relative to 100parts by mass of the crosslinkable elastomer.

A preferred amount of the non-oxide ceramic filler depends on theaverage particle size of the non-oxide ceramic filler. The amount of thenon-oxide ceramic filler having an average particle size of 0.01 to 0.1μm is more preferably 1 to 40 parts by mass, still more preferably 5 to25 parts by mass, relative to 100 parts by mass of the crosslinkableelastomer. The amount of the non-oxide ceramic filler having an averageparticle size of 0.1 to 10 μm is more preferably 5 to 50 parts by mass,still more preferably 10 to 30 parts by mass.

The non-oxide ceramic filler may be surface-oxidized by any method, suchas heat treatment in the air, acid treatment, ozone treatment, or oxygenplasma treatment.

The heat treatment may be performed under any conditions. Thetemperature for the heat treatment is preferably 500° C. to 1000° C.,more preferably 700° C. to 900° C. A temperature lower than 500° C.tends to cause less surface oxidation. A temperature higher than 1000°C. excessively tends to increase the surface oxidation rate to causedifficulty in controlling the thickness of the oxidized layer, resultingin excessive oxidation even inside the particles. The duration of theheat treatment is preferably 0.1 to 24 hours, more preferably 0.2 to 4hours.

Any acid may be used for the acid treatment, and examples thereofinclude sulfuric acid aqueous solution, hydrogen peroxide solution,nitric acid, a mixed acid of these. The acid treatment may be performedunder any conditions. The temperature for the treatment is preferably20° C. to 100° C., and the duration of the treatment is preferably 0.1to 24 hours, more preferably 0.2 to 4 hours.

The ozone treatment may be performed under any conditions, preferably atan ozone concentration of 100 to 300 g/N·m³, a discharge amount of 40 to80%, a cell pressure of 0.1 to 0.3 MPa, an O₂ flow rate of 2 to 5 L/min,a N₂ flow rate of 3 to 10 cc/min, and a temperature of 100° C. to 200°C.

The oxygen plasma treatment may be performed under any conditions,preferably at a power of 200 to 1000 W, an O₂ flow rate of 10 to 30sccm, a pressure of 1 to 5 Pa, an irradiation temperature of 20° C. to200° C., and an irradiation time of 0.1 to 1 hr.

The crosslinkable elastomer used may be a fluorine elastomer or asilicone elastomer. From the viewpoints of the heat resistance and theresistance to all types of plasma, a fluorine-containing elastomer ispreferred.

The fluorine-containing elastomer used in the invention may be any ofthose conventionally used for sealing materials, particularly sealingmaterials for semiconductor manufacturing devices.

Examples of the fluorine-containing elastomer include a fluoroelastomer(a), a thermoplastic fluoroelastomer (b) and a rubber compositioncontaining these fluoroelastomers.

Examples of the fluoroelastomer (a) include non-perfluorofluoroelastomer (a-1) and perfluoro fluoroelastomer (a-2).

Examples of the thermoplastic fluoroelastomer (b) include afluorine-containing multi-segmented polymer (b-1) containing anelastomeric fluorine-containing polymer chain segment and anon-elastomeric fluorine-containing polymer chain segment with at least90 mol % of the structural units of both the elastomericfluorine-containing polymer chain segment and the non-elastomericfluorine-containing polymer chain segment being perhalo olefins; afluorine-containing multi-segmented polymer (b-2) containing anelastomeric fluorine-containing polymer chain segment and anon-elastomeric fluorine-containing polymer chain segment with at least90 mol % of the structural units of the elastomeric fluorine-containingpolymer chain segment being perhalo olefins and with the non-elastomericfluorine-containing polymer chain segment containing less than 90 mol %of perhalo olefins as structural units; and a fluorine-containingmulti-segmented polymer (b-3) containing an elastomericfluorine-containing polymer chain segment and a non-elastomericfluorine-containing polymer chain segment with the elastomericfluorine-containing polymer chain segment containing less than 90 mol %of perhalo olefins as structural units and with non-elastomericfluorine-containing polymer chain segment containing 90 mol % or more ofperhalo olefins as structural units or containing less than 90 mol % ofperhalo olefins as structural units.

Examples of the non-perfluoro fluoroelastomer (a-1) include a vinylidenefluoride (VdF) fluoroelastomer, a tetrafluoroethylene (TFE)/propylenefluoroelastomer, a tetrafluoroethylene (TFE)/propylene/vinylidenefluoride (VdF) fluoroelastomer, an ethylene/hexafluoroethylene (HFP)fluoroelastomer, an ethylene/hexafluoroethylene (HFP)/vinylidenefluoride (VdF) fluoroelastomer, an ethylene/hexafluoropropylene(HFP)/tetrafluoroethylene (TFE) fluoroelastomer, a fluorosiliconefluoroelastomer, and a fluorophosphazene fluoroelastomer. These may beused alone or may be used in any combination as long as the effects ofthe invention are not impaired.

The vinylidene fluoride fluoroelastomer refers to a fluorine-containingelastic copolymer containing 45 to 85 mol % of vinylidene fluoride and55 to 15 mol % of at least one different monomer copolymerizable withvinylidene fluoride, preferably a fluorine-containing elastic copolymercontaining 50 to 80 mol % of vinylidene fluoride and 50 to 20 mol % ofat least one different monomer copolymerizable with vinylidene fluoride.

Examples of the at least one different monomer copolymerizable withvinylidene fluoride include fluorine-containing monomers such astetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE),trifluoroethylene, hexafluoropropylene (HFP), trifluoropropylene,tetrafluoropropylene, pentafluoropropylene, trifluorobutene,tetrafluoroisobutene, perfluoro(alkyl vinyl ether) (PAVE), and vinylfluoride and nonfluorine-containing monomers such as ethylene,propylene, and alkyl vinyl ether. These may be used alone or may be usedin any combination. Preferred among these are tetrafluoroethylene,hexafluoropropylene, and perfluoro(alkyl vinyl ether).

Specific examples of rubber include VdF-HFP rubber, VdF-HFP-TFE rubber,VdF-CTFE rubber, and VdF-CTFE-TFE rubber.

The vinylidene fluoride fluoroelastomer can be obtained by a usualmethod.

The tetrafluoroethylene/propylene fluoroelastomer refers to afluorine-containing elastic copolymer containing 45 to 70 mol % oftetrafluoroethylene, 55 to 30 mol % of propylene, and 0 to 5 mol % of amonomer that gives a crosslinking site.

Examples of the monomer that gives a crosslinking site includeiodine-containing monomers such asperfluoro(6,6-dihydro-6-iodo-3-oxa-1-hexene) andperfluoro(5-iodo-3-oxa-1-pentene) described in JP H05-63482 B and JPH07-316234 A, bromine-containing monomers described in JP H04-505341 A,monomers containing a nitrile group, monomers containing a carboxylgroup, and monomers containing an alkoxycarbonyl group described in JPH04-505345 A and JP H05-500070 A.

The tetrafluoroethylene/propylene fluoroelastomer can also be obtainedby a usual method.

These non-perfluoro fluoroelastomers (a-1) can be prepared by a usualmethod. Examples of commercially available products of the non-perfluorofluoroelastomer (a-1) include DAI-EL G-800 series and DAI-EL G-900series available from Daikin Industries, Ltd.

An example of the perfluoro fluororubber (a-2) is a copolymer containingtetrafluoroethylene and perfluoro(alkyl vinyl ether), such as afluorine-containing elastic copolymer containingtetrafluoroethylene/perfluoro(alkyl vinyl ether)/a monomer that gives acrosslinking site. The composition thereof is preferably (45 to 90)/(10to 50)/(0 to 5) (mol %), more preferably (45 to 80)/(20 to 50)/(0 to 5),further preferably (53 to 70)/(30 to 45)/(0 to 2). When the compositionis out of this range, the properties of a rubber elastic body tend to belost and the properties tend to become closer to those of resin.

Examples of the perfluoro(alkyl vinyl ether) in this case includeperfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether). Thesemay be used alone or may be used in any combination as long as theeffects of the invention are not impaired.

An example of the monomer that gives a crosslinking site is a monomerrepresented by the following formula:CY¹ ₂═CY²R_(f) ²X³(wherein Y¹ and Y² are each H, F, or CH₃; R_(f) ² is a linear orbranched fluorine-containing alkylene group whose hydrogen atoms arepartially or completely substituted with fluorine atoms and whichoptionally contains at least one oxygen atom as an ether bond andoptionally contains an aromatic ring; and X³ is an iodine group, abromine group, a nitrile group, a carboxyl group, an alkoxycarbonylgroup, an azide group, or an alkyne group). Specific examples thereofinclude an iodine-containing monomer represented by the followingformula (1):CX₂═CX—RfCHRI(wherein X is H, F, or CH₃; Rf is a fluoroalkylene group, aperfluoroalkylene group, a fluoropolyoxyalkylene group, or aperfluoropolyoxyalkylene group; and R is H or CH₃), and a monomerrepresented by the following formula (2):CF₂═CF(OCF₂CF(CF₃))_(m)—O—(CF₂)_(n)—X(wherein m is an integer of 0 to 5; n is an integer of 1 to 3; and X isa nitrile group, a carboxyl group, an alkoxycarbonyl group, a brominegroup, an azide group, or an alkyne group). These may be used alone ormay be used in any combination as long as the effects of the inventionare not impaired.

The iodine and nitrile groups can function as crosslinking sites.

The perfluoro fluoroelastomer (a-2) can be prepared by a usual method.

Specific examples of the perfluoro fluoroelastomer (a-2) includefluoroelastomers described in WO97/24381, JP S61-57324 B, JP H04-81608B, and JP H05-13961 B.

The fluorine-containing multi-segmented polymer (b-1) which is thethermoplastic fluoroelastomer (b) is described below. Thefluorine-containing multi-segmented polymer (b-1) contains anelastomeric fluorine-containing polymer chain segment and anon-elastomeric fluorine-containing polymer chain segment. At least 90mol % of the structural units of both the elastomericfluorine-containing polymer chain segment and the non-elastomericfluorine-containing polymer chain segment are perhalo olefins.

The elastomeric fluorine-containing polymer chain segment is described.The elastomeric fluorine-containing polymer chain segment impartsflexibility to the polymer and has a glass transition temperature of atmost 25° C., preferably at most 0° C. Examples of the perhalo olefinsthat constitute at least 90 mol % of the structural units thereofinclude tetrafluoroethylene, chlorotrifluoroethylene,hexafluoropropylene, and fluorovinylether represented by the followingformula (3):CF₂═CFO(CF₂CFYO)_(p)—(CF₂CF₂CF₂O)_(q)—Rf(wherein Y is F or CF₃; Rf is a C1-C5 perfluoroalkyl group; p is aninteger of 0 to 5; and q is an integer of 0 to 5).

Examples of the structural units other than the perhalo olefins thatconstitute the elastomeric fluorine-containing polymer chain segmentinclude fluorine-containing monomers such as vinylidene fluoride,trifluoroethylene, tetrafluoroethylene, trifluoropropylene,tetrafluoropropylene, pentafluoropropylene, trifluorobutene,tetrafluoroisobutene, and vinyl fluoride and nonfluorine-containingmonomers such as ethylene, propylene, and alkyl vinyl ether.

A preferred example of the elastomeric fluorine-containing polymer chainsegment is an elastic polymer chain containingtetrafluoroethylene/perfluoro(alkyl vinyl ether)/a monomer that gives acrosslinking site. The composition thereof is preferably (50 to 85)/(50to 15)/(0 to 5) (mol %).

An example of the monomer that gives a crosslinking site is a monomerrepresented by the following formula:CY¹ ₂═CY²R_(f) ²X²(wherein Y¹ and Y² are each H, F, or CH₃; R_(f) ² is a linear orbranched fluorine-containing alkylene group whose hydrogen atoms arepartially or completely substituted with fluorine atoms and whichoptionally contains at least one oxygen atom as an ether bond andoptionally contains an aromatic ring; and X³ is an iodine group, abromine group, a nitrile group, a carboxyl group, an alkoxycarbonylgroup, an azide group, or an alkyne group). Specific examples thereofinclude an iodine-containing monomer represented by the followingformula (4):CX₂═CX—RfCHRX¹(wherein X is H, F, or CH₃; Rf is a fluoroalkylene group, aperfluoroalkylene group, a fluoropolyoxyalkylene group, or aperfluoropolyoxyalkylene group; R is H or CH₃; and X¹ is iodine orbromine), and a monomer represented by the following formula (5):CF₂═CF(OCF₂CF(CF₃))_(m)—O—(CF₂)_(n)—X(wherein m is an integer of 0 to 5; n is an integer of 1 to 3; and X isa nitrile group, a carboxyl group, an alkoxycarbonyl group, a brominegroup, an azide group, or an alkyne group).

The iodine, bromine, nitrile, carboxyl, and alkoxycarbonyl groups canfunction as crosslinking sites.

The non-elastomeric fluorine-containing polymer chain segment isdescribed. Examples of the perhalo olefins that constitute at least 90mol % of the structural units of the non-elastomeric fluorine-containingpolymer chain segment include perhalo olefins such astetrafluoroethylene, chlorotrifluoroethylene, perfluoro(alkyl vinylether), hexafluoropropylene, a compound represented by the followingformula (6):CF₂═CF(CF₂)_(p)X(wherein p is an integer of 1 to 10; and X is F or Cl), andperfluoro-2-butene.

Examples of the structural units other than the perhalo olefins thatconstitute the non-elastomeric fluorine-containing polymer chain segmentinclude fluorine-containing monomers such as vinylidene fluoride,trifluoroethylene, tetrafluoroethylene, trifluoropropylene,tetrafluoropropylene, pentafluoropropylene, trifluorobutene,tetrafluoroisobutene, and vinyl fluoride and nonfluorine-containingmonomers such as ethylene, propylene, and alkyl vinyl ether.

A preferred example of the non-elastomeric fluorine-containing polymerchain segment is a nonelastic polymer chain containing 85 to 100 mol %of tetrafluoroethylene and 0 to 15 mol % of a monomer represented by thefollowing formula (7):CF₂═CF—Rf(wherein Rf is Rf¹ or —ORf¹; and Rf¹ is a C1-C5 perfluoroalkyl group).

From the viewpoint of the heat resistance of the thermoplasticfluoroelastomer (fluorine-containing multi-segmented polymer) to beobtained, the crystal melting point of the non-elastomericfluorine-containing polymer chain segment is at least 150° C.,preferably 200° C. to 360° C.

That is, what is important is that the fluorine-containingmulti-segmented polymer (b-1) is a fluorine-containing multi-segmentedpolymer in which an elastomeric fluorine-containing polymer chainsegment and a non-elastomeric fluorine-containing polymer chain segmentare bonded by blocking or grafting in each molecule.

Accordingly, the fluorine-containing multi-segmented polymer (b-1) maybe produced by a variety of known processes in which an elastomericsegment and a non-elastomeric segment are connected by blocking orgrafting to form a fluorine-containing multi-segmented polymer.Particularly, the process for preparing a block-type fluorine-containingmulti-segmented polymer described in JP S58-04728 B and the process forpreparing a graft-type fluorine-containing multi-segmented polymerdescribed in JP S62-34324 A are preferably employed.

In order to obtain a homogeneous and regular segmented polymer having ahigh segmentation percentage (block percentage), particularly preferredis a block-type fluorine-containing multi-segmented polymer synthesizedby the iodine transfer polymerization method described in JP S58-04728 Band KOBUNSHI RONBUNSHU Japanese Journal of Polymer Science andTechnology (Vol. 49, No. 10, 1992).

A mere mixture of an elastomeric fluorine-containing polymer and anon-elastomeric fluorine-containing polymer may usually haveinsufficient mechanical properties (particularly at high temperatures)and reduced abrasion resistance, flexibility, and durability, althoughthe effects differ according to the type, mixing properties, andcompatibility of each polymer mixed.

On the other hand, a multi-segmented polymer prepared by bonding anelastomeric segment and a non-elastomeric segment by blocking orgrafting can have improved heat resistance and mechanical properties(particularly at high temperatures) in comparison to the mere mixture ofan elastomeric fluorine-containing polymer and a non-elastomericfluorine-containing polymer.

The elastomeric segment can be prepared by the iodine transferpolymerization method, which is known as a process for preparing afluoroelastomer (JP S58-04728 B, JP S62-12734 A). An example is a methodof emulsion polymerizing a perhalo olefin and, if necessary, a monomerthat gives a crosslinking site using a radical initiator in an aqueousmedium with an iodine compound, preferably a diiodine compound, in asubstantially oxygen-free atmosphere, while stirring the component underpressure. Typical examples of the diiodine compound used include1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane,1,3-diiodo-2-chloroperfluoropropane,1,5-diiodo-2,4-dichloroperfluoropentane, 1,6-diiodoperfluorohexane,1,8-diiodoperfluorooctane, 1,12-diiodoperfluorododecane,1,16-diiodoperfluorohexadecane, diiodomethane, and 1,2-diiodoethane.These compounds may be used alone or may be used in combination.Preferred among these is 1,4-diiodoperfluorobutane. The amount of thediiodine compound is 0.01 to 1% by mass relative to the total mass ofthe elastomeric segment.

The elastomeric segment obtained in this way has a perhalo-type terminaland has an iodine atom that is the initiation point of blockcopolymerization of the non-elastomeric segment.

The radical polymerization initiator used for preparing the elastomericsegment in the invention may be an initiator conventionally used forproduction of a fluorine elastomer by polymerization. Examples of suchan initiator include organic and inorganic peroxides and azo compounds.Examples of typical initiators include persulfates, carbonate peroxides,and ester peroxides, and a preferred initiator is ammonium persulfate(APS). APS may be used alone or may be used in combination with areducing agent such as a sulfite or a sulfurous acid salt.

The elastomeric segment obtained in this way preferably has a numberaverage molecular weight of 5,000 to 750,000, particularly 20,000 to400,000, from the viewpoint of imparting flexibility, elasticity, andmechanical properties to the entire fluorine-containing multi-segmentedpolymer.

Subsequently, block copolymerization of the non-elastomeric segment canbe performed subsequent to the emulsion polymerization of theelastomeric segment by changing the monomer into those for thenon-elastomeric segment.

The number average molecular weight of the non-elastomeric segment canbe adjusted within a wide range of 1,000 to 1,200,000, preferably 3,000to 600,000.

The fluorine-containing multi-segmented polymer (b-1) obtained in thisway is composed mainly of polymer molecules in which non-elastomericsegments are bonded to both sides of the elastomeric segment and polymermolecules in which non-elastomeric segments are bonded to one side ofthe elastomeric segment. The amount of polymer molecules consisting ofelastomeric segments and containing no elastomeric segments bondedthereto is at most 20% by mass, preferably at most 10% by mass, relativeto the total amount of the segments and the polymer molecules in thefluorine-containing multi-segmented polymer.

The fluorine-containing multi-segmented polymer (b-2) is describedbelow. The fluorine-containing multi-segmented polymer (b-2) contains anelastomeric fluorine-containing polymer chain segment and anon-elastomeric fluorine-containing polymer chain segment. At least 90mol % of the structural units of the elastomeric fluorine-containingpolymer chain segment are perhalo olefins and the non-elastomericfluorine-containing polymer chain segment contains less than 90 mol % ofperhalo olefins as structural units.

The elastomeric fluorine-containing polymer chain segment thereof is thesame as that given for the fluorine-containing multi-segmented polymer(b-1).

The non-elastomeric fluorine-containing polymer chain segment is apolymer chain having a crystal melting point of at least 150° C.,preferably 200° C. to 360° C.

Examples of the structural units of the non-elastomericfluorine-containing polymer chain segment include vinylidene fluoride,vinyl fluoride, trifluoroethylene, a compound represented by thefollowing formula (8):CH₂═CX—(CF₂)_(q)—X(wherein X is H or F; and q is an integer of 1 to 10), and partiallyfluorinated olefins such as CH₂═C(CF₃)₂.

Also, monomers that are copolymerizable with these monomers, such asethylene, propylene, vinyl chloride, vinyl ether, vinyl carboxylate, andacrylic acid may be used as copolymerization components.

The fluorine-containing multi-segmented polymer (b-2) can be prepared inthe same manner as the fluorine-containing multi-segmented polymer(b-1).

The fluorine-containing multi-segmented polymer (b-3) is describedbelow. The fluorine-containing multi-segmented polymer (b-3) contains anelastomeric fluorine-containing polymer chain segment and anon-elastomeric fluorine-containing polymer chain segment. Theelastomeric fluorine-containing polymer chain segment contains less than90 mol % of perhalo olefins as structural units and at least 90 mol % ofthe structural units of the non-elastomeric fluorine-containing polymerchain segment are perhalo olefins or the non-elastomericfluorine-containing polymer chain segment contains less than 90 mol % ofperhalo olefins as structural units.

The elastomeric fluorine-containing polymer chain segment of thefluorine-containing multi-segmented polymer (b-3) is a polymer chainhaving a glass transition point of at most 25° C., preferably at most 0°C.

The elastomeric fluorine-containing polymer chain segment contains lessthan 90 mol % of perhalo olefins as structural units. Examples of thestructural units other than the perhalo olefins are the same as thosegiven for the vinylidene fluoride fluoroelastomer, which is anon-perfluoro fluoroelastomer (a-1).

The non-elastomeric fluorine-containing polymer chain segment of thefluorine-containing multi-segmented polymer (b-3) is the same as thenon-elastomeric fluorine-containing polymer chain segment in thefluorine-containing multi-segmented polymer (b-1) or (b-2), preferablythe same as the non-elastomeric fluorine-containing polymer chainsegment in (b-2).

The fluorine-containing multi-segmented polymer (b-3) contains 40 to 95%by mass of the elastomeric fluorine-containing polymer chain segment and5 to 60% by mass of the non-elastomeric fluorine-containing polymerchain segment.

The fluorine-containing multi-segmented polymer (b-3) can be prepared inthe same manner as the fluorine-containing multi-segmented polymers(b-1) and (b-2).

Specific examples of the fluorine-containing multi-segmented polymer(b-3) include DAI-EL Thermo T-530, T-550, and T-630 available fromDaikin Industries, Ltd. and CEFRAL SOFT available from Central GlassCo., Ltd.

In the invention, a composition containing the fluoroelastomer (a) andthe thermoplastic fluoroelastomer described above may be used.

A first fluoroelastomer composition containing the non-perfluorofluoroelastomer (a-1) and the fluorine-containing multi-segmentedpolymer (b-1) can be obtained by mixing the non-perfluorofluoroelastomer (a-1) and the fluorine-containing multi-segmentedpolymer (b-1) at any ratio in the form of dispersion or by dry blendingthese at any ratio with an open roll.

Also, in order to improve the mold release properties in molding,additives such as an internal mold release agent may be added asappropriate as long as the effects of the invention are not impaired.

A second fluoroelastomer composition containing the non-perfluorofluoroelastomer (a-1) and the fluorine-containing multi-segmentedpolymer (b-2) can be obtained in the same manner as the firstfluoroelastomer composition.

The above additive may be added as appropriate as long as the effects ofthe invention are not impaired and a cross-linking agent may be added inaccordance with the type of the crosslinking method described below.

A third fluoroelastomer composition containing the perfluorofluoroelastomer (a-2) and the fluorine-containing multi-segmentedpolymer (b-3) can be obtained in the same manner as the firstfluoroelastomer composition.

The above additive may be added as appropriate as long as the effects ofthe invention are not impaired and a cross-linking agent may be added inaccordance with the type of the crosslinking method described below.

A fourth fluoroelastomer composition containing the perfluorofluoroelastomer (a-2) and the fluorine-containing multi-segmentedpolymer (b-1) can be obtained in the same manner as the firstfluoroelastomer composition.

Both the perfluoro fluoroelastomer (a-2) and the fluorine-containingmulti-segmented polymer (b-1) are poor in crosslinking efficiency byradiation and substantially cannot be crosslinked by radiation.Therefore, a crosslinking site which enables peroxide crosslinking, forexample, needs to be introduced into at least one of the rubbers forcrosslinking.

A preferred example of the fluoroelastomer with a crosslinking siteintroduced therein is a fluoroelastomer with iodine or bromineintroduced into a polymer terminal. This fluoroelastomer is obtained byintroducing a compound represented by the following formula (9):RI_(x)Br_(y)(wherein R is a C1-C16 saturated or unsaturated fluorohydrocarbon orchlorofluorohydrocarbon group or a C1-C3 hydrocarbon group; and x and yare each an integer of 0 to 2 and 1≤x+y≤2) in preparation bypolymerization. The iodine or bromine that is introduced in this wayfunctions as a crosslinking site.

Examples of the compound represented by the following formula (9):RI_(x)Br_(y)(wherein R is a C1-C16 saturated or unsaturated fluorohydrocarbon orchlorofluorohydrocarbon group or a C1-C3 hydrocarbon group; and x and yare each an integer of 0 to 2 and 1≤x+y≤2) include1,3-diiodoperfluoropropane, 1,3-diiodo-2-chloroperfluoropropane,1,4-diiodoperfluorobutane, 1,5-diiodo-2,4-dichloroperfluoropentane,1,6-diiodoperfluorohexane, 1,8-diiodoperfluorooctane,1,12-diiodoperfluorododecane, 1,16-diiodoperfluorohexadecane,diiodomethane, 1,2-diiodoethane, 1,3-diiodo-n-propane, CF₂Br₂,BrCF₂CF₂Br, CF₃CFBrCF₂Br, CFClBr₂, BrCF₂CFClBr, CFBrClCFClBr,BrCF₂CF₂CF₂Br, BrCF₂CFBrOCF₃, 1-bromo-2-iodoperfluoroethane,1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane,2-bromo-3-iodoperfluoroebutane,3-bromo-4-iodoperfluorobutene-1,2-bromo-4-iodoperfluorobutene-1,monoiodomonobromo-substituted benzene, diiodomonobromo-substitutedbenzene, and (2-iodoethyl)-substituted benzene and(2-bromoethyl)-substituted benzene.

From the viewpoints of properties such as polymerization reactivity,crosslinking reactivity, and easy availability, preferably used amongthese are 1,4-diiodoperfluorobutane and diiodomethane.

The amount of the compound represented by the following formula (9):RI_(x)Br_(y)(wherein R is a C1-C16 saturated or unsaturated fluorohydrocarbon orchlorofluorohydrocarbon group or a C1-C3 hydrocarbon group; and x and yare each an integer of 0 to 2 and 1≤x+y≤2) is 0.0001 to 5% by mass,preferably 0.01 to 1% by mass of the total mass of the fluoroelastomerto be obtained.

Another method for introducing a crosslinking site is a method ofcopolymerizing a small amount of a monomer that gives a crosslinkingsite.

Preferred examples of such a monomer include iodine-containing monomerssuch as perfluoro(6,6-dihydro-6-iodo-3-oxa-1-hexene) andperfluoro(5-iodo-3-oxa-1-pentene) described in JP H05-63482 B and JPH07-316234 A, bromine-containing monomers described in JP H04-505341 A,a monomer containing a nitrile group, a monomer containing a carboxylgroup, and a monomer containing an alkoxycarbonyl group described in JPH04-505345 A and JP H05-500070 A.

A fifth fluoroelastomer composition containing the perfluorofluoroelastomer (a-2) and the fluorine-containing multi-segmentedpolymer (b-2) can be obtained in the same manner as the firstfluoroelastomer composition.

The above additive may be added as appropriate as long as the effects ofthe invention are not impaired and a cross-linking agent may be added inaccordance with the type of the crosslinking method described below.

The monomer mixed gas used in the invention is explosive, as describedby G. H. Kalb et al., in Advances in Chemistry Series, 129, 13 (1973),and the polymerization device needs to be designed so that sparks, whichbecome an ignition source, are not generated. In light of this, thepolymerization pressure is preferably kept as low as possible.

The polymerization pressure can be changed in a wide range and isusually within the range of 0.5 to 5 MPa. The higher the polymerizationpressure is, the higher the polymerization rate is. Thus, in order toimprove the productivity, the polymerization pressure is preferably atleast 0.8 MPa.

Some of the polymerization products obtained in this way under certainpolymerization conditions may contain no free carboxyl groups. Still,the following acid treatment enables conversion into free carboxylgroups.

Examples of the silicone elastomer used in the invention includesilicone rubber and fluorosilicone rubber.

Preferred among the crosslinkable elastomers obtained in this way as thefluorine-containing elastomer used in the invention is a copolymercontaining tetrafluoroethylene/perfluoro(alkyl vinyl ether)/a monomerhaving a crosslinkable functional group, from the viewpoints of heatresistance and chemical resistance.

Examples of the perfluoro(alkyl vinyl ether) include perfluoro(methylvinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), andperfluoro(propyl vinyl ether) (PPVE). Preferred among these is PMVEbecause it has excellent cold resistance.

From the viewpoint of the copolymerization reactivity, the monomer forintroducing a crosslinking site is preferably an iodine-containingmonomer, a monomer containing a nitrile group, a monomer containing acarboxyl group, or a monomer containing an alkoxycarbonyl group. Amonomer containing a nitrile group is more preferred from the viewpointsof the crosslinking reactivity and the heat resistance of thecrosslinking structure formed by the crosslinking reaction.

An example of the method for introducing a carboxyl group, analkoxycarbonyl group, an iodine atom, a bromine atom, or a sulfonic acidgroup into a polymer terminal group of the crosslinkable elastomer isthe acid treatment described below.

The above crosslinkable elastomer can be prepared by polymerizationmethods such as emulsion polymerization, suspension polymerization, andsolution polymerization.

The emulsifier used for emulsion polymerization may be selected from awide range. In order to inhibit the chain transfer reaction to theemulsifier molecules that occurs during the polymerization, preferredare salts of a carboxylic acid having a fluorocarbon chain or afluoropolyether chain. The amount of the emulsifier is preferably about0.05 to 2% by mass, more preferably 0.2 to 1.5% by mass of the amount ofwater that is added.

The polymerization initiator used for production of the crosslinkableelastomer by polymerization is preferably an initiator capable ofintroducing a carboxyl group or a group capable of producing a carboxylgroup (e.g., acid fluoride, acid chloride, CF₂OH, all of which produce acarboxyl group in the presence of water) into an elastomer terminal.Specific examples include ammonium persulfate (APS) and potassiumpersulfate (KPS).

A chain transfer agent that is usually used to adjust the molecularweight may be used, but is preferably used as little as possible becauseit reduces the proportion of the group capable of producing a carboxylor alkoxycarbonyl group that is introduced a terminal. However, thisdoes not apply when the chain transfer agent is capable of introducingthe above group into an elastomer terminal. When a chain transfer agentis not used, the molecular weight can be adjusted by performingpolymerization under low pressure, for example less than 2 MPa·G, morepreferably at most 1 MPa·G. Other polymerization conditions are notlimited. However, in order to produce a polymerization product having acarboxyl group in a terminal and/or a branched chain without the acidtreatment described below, the pH of the polymerization system ispreferably set to at most 3, i.e., a strong acidic value.

With respect to the crosslinkable elastomer used in the invention,groups such as a metallic salt and ammonium salt of a carboxylic acidthat are present in the polymerization product are preferably convertedinto carboxyl groups by acid treatment on the polymerization product.Suitable methods for acid treatment include a method of cleaning withhydrochloric acid, sulfuric acid, or nitric acid and a method ofadjusting the pH of the system of a mixture after the polymerizationreaction to at most 3 with these acids.

In order to simplify the process, this acid treatment is preferablyapplied as an agglomeration technique for isolating the polymerizationproduct from the polymerization reaction mixture by agglomeration. Also,the polymerization mixture may be subjected to acid treatment and thenthe polymer product may be isolated by lyophilization, for example.Furthermore, a method of agglomeration by ultrasonic waves or mechanicalpower may be employed.

A carboxyl group may be introduced by oxidizing a crosslinkableelastomer containing iodine or bromine with fuming nitric acid.

Examples of the curing agent used in the invention include peroxidecrosslinking curing agents, polyol crosslinking curing agents, polyaminecrosslinking curing agents, triazine crosslinking curing agents, oxazolecrosslinking curing agents, imidazole crosslinking curing agents,thiazole crosslinking curing agents, and radiation crosslinking curingagents.

The curing agent used in peroxide crosslinking is an organic peroxidethat can easily produce a peroxy radical in the presence of heat or aredox system. Specific examples thereof include1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane,2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide (PerbutylD), t-butylcumyl peroxide (Perbutyl C), dicumyl peroxide (Percumyl D,Percumyl D-40, Percumyl D-40 MB(T)),α,α-bis(t-butylperoxy)-p-diisopropylbenzene,2,5-dimethyl-2,5-di(t-butylperoxy)hexane (Perhexa 25B, Perhexa 25B-40),2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 (Perhexyne 25B, Perhexyne25B-40), benzoyl peroxide, t-butylperoxybenzene,2,5-dimethyl-2,5-di(benzoylperoxy)hexane (Perhexa 25Z), t-butylperoxymaleate (t-butyl MA), t-butylperoxyisopropyl carbonate (Perbutyl 1-75),methyl ethyl ketone peroxide (Permek D (DR), Permek H (HR, HY), Permek N(NR, NY), Permek S (SR), Permek F (FR), Permek G (GR, GY)),cyclohexanone peroxide (Perhexa H), acetylacetone peroxide (Percure AH,AL), 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane (Perhexa TMH),1,1-di(t-hexylperoxy)cyclohexane (Perhexa HC),1,1-di(t-butylperoxy)-2-methyl cyclohexane (Perhexa MC),1,1-di(t-butylperoxy)cyclohexane (Perhexa C-80(S), Perhexa C-75(EB),Perhexa C(C), Perhexa C-40, Perhexa C-40 MB(S)),2,2-di(t-butylperoxy)butane (Perhexa 22), butyl 4,4-di-(t-butylperoxy)pentanoate (Perhexa V, Perhexa V-40(F)),2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane (Pertetra A), p-menthanehydroperoxide (Permentha H), diisopropylbenzene hydroperoxide (PercumylP), 1,1,3,3-tetramethylbutyl hydroperoxide (Perocta H), cumenehydroperoxide (Percumyl H-80), t-butyl hydroperoxide (Perbutyl H-69),di(2-t-butylperoxyisopropyl)benzene (Perbutyl P, Perbutyl P-40,Peroxymon F-40, Perbutyl P-40 MB(K)), di-t-hexyl peroxide (Perhexyl D),diisobutyryl peroxide (Peroyl IB), di(3,5,5-trimethylhexanoyl) peroxide(Peroyl 355(S)), dilauroyl peroxide (Peroyl L), disuccinic peroxide(Peroyl SA), a mixture of di-(3-methylbenzoyl) peroxide,benzoyl(3-methylbenzoyl) peroxide, and dibenzoyl peroxide (NyperBMT-K40, Nyper BMT-M), dibenzoyl peroxide (Nyper BW, Nyper BO, Nyper FF,Nyper BS, Nyper E, Nyper NS), di(4-methylbenzoyl) peroxide (Nyper PMB),di-n-propyl peroxydicarbonate (Peroyl NPP-50M), diisopropylperoxydicarbonate (Peroyl IPP-50, Peroyl IPP-27),di(4-t-butylcyclohexyl) peroxydicarbonate (Peroyl TCP), di(2-ethylhexyl)peroxydicarbonate (Peroyl OPP), di-sec-butylperoxydicarbonate (PeroylSBP), cumyl peroxyneodecanoate (Percumyl ND, Percumyl ND-50E),1,1,3,3-tetramethylbutylperoxyneodecanoate (Perocta ND, Perocta ND-50E),t-hexyl peroxyneodecanoate (Perhexyl ND, Perhexyl ND-50E),t-butylperoxyneodecanoate (Perbutyl ND, Perbutyl ND-50E), t-butylperoxyneoheptanoate (Perbutyl NHP), t-hexylperoxy pivalate (Perhexyl PV,Perhexyl PV-50E), t-butylperoxy pivalate (Perbutyl PV, Perbutyl PV-40E),1,1,3,3-tetramethylbutylperoxy-2-ethyl hexanoate (Perocta 0),2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (Perhexa 250), t-hexylperoxy-2-ethyl hexanoate (Perhexyl O, Percure HO(N)),t-butylperoxy-2-ethyl hexanoate (Perbutyl O, Percure O), t-hexylperoxyisopropyl monocarbonate (Perhexyl I),t-butylperoxy-3,5,5-trimethyl hexanoate (Perbutyl 355), t-butylperoxylaurate (Perbutyl L), t-butylperoxy-2-ethylhexyl monocarbonate (PerbutylE), t-hexyl peroxybenzoate (Perhexyl Z), t-butyl peroxyacetate (PerbutylA), a mixture of t-butylperoxy-3-methyl benzoate and t-butylperoxybenzoate (Perbutyl ZT), t-butylperoxy benzoate (Perbutyl Z),t-butylperoxyallyl monocarbonate (peromer AC),3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone (BTTB-25), and2,3-dimethyl-2,3-diphenylbutane (Nofmer BC-90). Preferred among theseare dialkyl curing agents, and particularly preferred is2,5-dimethyl-2,5-di(t-butylperoxy)hexane. Usually, the type and amountof the organic peroxide are selected in consideration of the amount ofactive —O—O— and the decomposition temperature.

The curing aid to be used in this case is a compound having reactivitywith a peroxy radical and a polymer radical. Examples thereof includemultifunctional compounds containing a functional group such as CH₂═CH—,CH₂═CHCH₂—, CF₂═CF—, CF₂═C(CF₃)—, CF₂═C(CH₃)—, CF(CF₃)═CF—, CF(CH₃)═CF—,CF₂═C(C₆H₅)—, CF(C₆H₅)═CF—, CF₂═CH—, CHF═CF—, CHF═C(CF₃)—, CH(CF₃)═CF—,and CF(CF₃)═CH— (“C₆H₅” in each formula represents a phenyl group).Specific examples thereof include triallyl cyanurate, triallylisocyanurate (TAIC), triacrylformal, triallyl trimellitate,N,N′-n-phenylene bismaleimide, dipropargyl terephthalate, diallylphthalate, tetraallyl terephthalate amide, triallyl phosphate,bismaleimide, fluorinated triallyl isocyanurate(1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine-2,4,6-trione),tris(diallylamine)-S-triazine, triallyl phosphite, N,N-diallylacrylamide, 1,6-divinyl dodecafluorohexane, and a compound representedby the following formula (I):

(wherein R₁, R₂, R₃, R₄, R₅, and R₆ are the same as or different fromeach other and are each H, halogen, or an optionally halogenated groupoptionally containing one or multiple oxygen groups; and Z is a linearor branched optionally halogenated alkylene group optionally containinga hetero atom, a cycloalkylene group, an arylene group, or a (per)fluoropolyoxyalkylene group).

Examples of the compound represented by the formula (I) include:

a compound represented by the following formula (II):

(wherein A^(II) is a single bond, a hetero atom-containing group, alinear or branched alkylene group, a cycloalkylene group, or an arylenegroup, and each of these groups may be partially or completelyfluorinated; R^(II1) is an alkyl group; R^(II2) and R^(II3) are eachindependently a hydrogen atom, a fluorine atom, an alkyl group, afluorinated alkyl group, or a substituted or non-substituted aryl group;multiple Rills may be the same as or different from each other; multipleR^(II2)s may be the same as or different from each other; multipleR^(II3)s may be the same as or different from each other; at least oneselected from R^(II2) and R^(II3) is a fluorine atom or a groupcontaining a fluorine atom; ns are each an integer of 1 to 5; andhydrogen atom(s) in each benzene ring may be substituted);

a compound represented by the following formula (III):

(wherein j is an integer of 2 to 10, preferably 4 to 8; and R^(III1),R^(III2), R^(III3), and R^(III4) are the same as or different from eachother and are each H, F, a C₁-C₅ alkyl group, or a (per)fluoroalkylgroup);

a compound represented by the following formula (IV):

(wherein A^(IV)s are the same as or different from each other and ateach occurrence and are each independently selected from F, Cl, and H;B^(IV)s are the same as or different from each other and at eachoccurrence and are each independently selected from F, Cl, H, andOR^(BIV) (wherein R^(BIV) is a branched or linear alkyl group that maybe partially, substantially, or completely fluorinated or chlorinated);E^(IV) is an optionally fluorinated C2-C10 bivalent group optionallycontaining an ether bond; E^(IV) is preferably a group represented by—(CF₂)_(m)— wherein m is an integer of 3 to 5; and the compoundrepresented by the formula (IV) is preferably F₂C═CF—O—(CF₂)₅—O—CF═CF₂);

a compound by the following formula (V):

(wherein E^(V), A^(V), and B^(V) are the same as the above definedE^(IV), A^(IV), and B^(IV), respectively; and R^(V5), R^(V6), and R^(V7)are the same as or different from each other and are each H, F, a C₁-C₅alkyl group, or a (per)fluoroalkyl group); and a compound containing atleast one structure represented by the following formula (VI):

(wherein R^(VI1) to R^(VI3) are each independently a hydrogen atom, afluorine atom, an alkyl group, a fluorinated alkyl group, or asubstituted or non-substituted aryl group, at least one selected fromR^(VI1) to R^(VI3) is a fluorine atom or a group containing a fluorineatom; m is an integer of 1 to 5; when m is 2 or greater, the m R^(VI1)sto R^(VI3)s are the same as or different from each other; and hydrogenatom(s) in the benzene ring may be substituted). When m is 1, thecompound preferably contains two or more of the structures. The heteroatom-containing group is a group containing a hetero atom other than acarbon atom. Examples of the hetero atom include an oxygen atom, anitrogen atom, and a sulfur atom. Examples of the hetero atom-containinggroup include —O—, —S—, —SO₂—, and —CO—.

An example of the compound represented by the formula (VI) is a compoundrepresented by the following formula:

(wherein R^(VI1) to R^(VI3) are as defined above; p is an integer of 0to 2; and n is an integer of 2 to 6).

Examples of the curing agent used in polyol crosslinking includepolyhydric alcohol compounds such as bisphenol A and bisphenol AF.

Examples of the curing agent used in polyamine crosslinking includepolyamine compounds such as hexamethylenediamine carbamate,N,N′-dicinnamylidene-1,6-hexanediamine, and4,4′-bis(aminocyclohexyl)methanecarbamate.

Examples of the curing agent used in triazine crosslinking includeorganic tin compounds such as tetraphenyl tin and triphenyl tin. Inorder to cause a cyclotrimerization reaction of cyano groups in thefluorine-containing elastomer and thereby to proceed a triazinecrosslinking reaction, a non-oxide filler such as silicon nitride mayalso be used.

Examples of the curing agent used in oxazole crosslinking, imidazolecrosslinking, and thiazole crosslinking include a bisdiaminophenylcuring agent, a bisaminophenol curing agent, and a bisaminothiophenolcuring agent, each represented by the following formula (10):

(wherein R¹ is —SO₂—, —O—, —CO—, a C1-C6 alkylene group, a C1-C10perfluoroalkylene group, or a single bond; and one selected from R² andR³ is —NH₂ and the other is —NH₂, —OH or —SH, preferably both R² and R³are —NH₂), a bisamidrazone curing agent represented by the followingformula (11):

(wherein R1 is defined as described above, R4 is

a bisamidoxime curing agent represented by the following formula (12) or(13):

(wherein Rf is a C1-C10 perfluoroalkylene group),

(wherein n is an integer of 1 to 10), and a compound represented by thefollowing formula (VI):R^(VI1)N═CR^(VI2)R^(VI3)  (VI)(wherein R^(VI1) is H; R^(VI2) is selected from the group consisting ofH, NH₂, and NR^(VI4)R^(VI5); R^(VI3) is selected from the groupconsisting of Ph, SO₂H, NR^(VI6)R^(VI7), 2-pyridine, and CH₂CONH₂;R^(VI4) is H; R^(VI5) is selected from the group consisting of Ph, NH₂,and CN; R^(VI6) is selected from the group consisting of H, NHPh,CCONH₂, a C1-C8 linear alkyl group, and a C1-C8 branched alkyl group;and R″⁷ is selected from the group consisting of Ph, COOC(CH₃)₃, NH₂,CH₂COOH, CSNH₂, CNHNH₃ ⁺Cl⁻, p-phenyl CN, COPh, and compoundsrepresented by the following formulas:

These bisaminophenol curing agent, bisaminothiophenol curing agent, andbisdiaminophenyl curing agent have been conventionally used in acrosslinking system in which the crosslinking site is a nitrile group,and also react with a carboxyl group and an alkoxycarbonyl group andform an oxazole ring, thiazole ring, and an imidazole ring,respectively, to give a crosslinked article.

From the viewpoints of particularly excellent heat resistance, favorablecrosslinking reactivity, and relatively easy synthesis, more preferredamong these curing agents is a bisdiaminophenyl curing agent having atleast two bisamino crosslinkable functional groups represented by thefollowing formula (14):

(wherein R⁵ is a fluorine atom or a monovalent organic group). Examplesof a functional group that can be reacted with the crosslinkablefunctional groups include a nitrile group, a carboxyl group, and analkoxycarbonyl group, and an imidazole ring is formed by the reaction.

A still more preferred curing agent is a compound represented by thefollowing formula (15):

The substitutent R⁶ in each crosslinkable reactive group is a monovalentorganic group other than hydrogen or a fluorine atom, and a substitutentthat forms an N—R⁶ bond having higher oxidization resistance than an N—Hbond is particularly preferred. Herein, “a substitutent that forms anN—R⁶ bond having higher oxidization resistance than an N—H bond” refersto a substitutent that forms an N—R⁶ bond that is present in a compoundthat is less likely to be oxidized than a compound having an N—H bondwhen an imidazole ring is formed.

Examples of such R⁶ include, but are not limited to, an aliphatichydrocarbon group that may be substituted, a phenyl group that may besubstituted, or a benzyl group.

Specific examples include compounds wherein at least one R⁶ is a loweralkyl group having 1 to 10, preferably 1 to 6 carbon atoms, such as—CH₃, —C₂H₅, and —C₃H₇; a fluorine-containing lower alkyl group having 1to 10, preferably 1 to 6 carbon atoms, such as —CF₃, —C₂F₅, —CH₂F,—CH₂CF₃, and —CH₂C₂F₅; a phenyl group; a benzyl group; a phenyl group ora benzyl group wherein 1 to 5 hydrogen atoms are each substituted with afluorine atom, such as —C₆F₅ and —CH₂C₆F₅; and a phenyl or benzyl groupwherein 1 to hydrogen atoms are each substituted with —CF₃, such as—C₆H₅-n(CF₃)_(n) and —CH₂C₆H₅-n(CF₃)_(n) (wherein n is an integer of 1to 5).

Preferred among these are a phenyl group and —CH₃ from the viewpoints ofparticularly excellent heat resistance, favorable crosslinkingreactivity, and relatively easy synthesis.

In the compound represented by the formula (15), R⁷ is —SO₂—, —O—, —CO—,an alkylene group that may be substituted,

or a single bond.

Preferred specific examples of the alkylene group that may besubstituted for R⁷ include, but are not limited to, a C1-C6nonsubstituted alkylene group and a C1-C10 perfluoroalkylene group. Anexample of the perfluoroalkylene group is

These examples of R⁷ are known as examples of bisdiaminophenyl compoundsfrom JP H02-59177 B and JP H08-120146 A.

R⁷ may be bonded to any position of both the right and left benzenerings. From the viewpoint of easy synthesis and easy progress of acrosslinking reaction, either an —NH₂ group or an —NHR⁷ is preferablybonded at the para position.

A particularly preferred example of the curing agent is a compoundrepresented by the following formula (16):

(wherein R⁸s are the same or different from each other and are each aC1-C10 alkyl group, a C1-C10 alkyl group containing a fluorine atom, aphenyl group, a benzyl group, or a phenyl or benzyl group wherein 1 to 5hydrogen atoms are each substituted with a fluorine atom or —CF₃).

Examples thereof include, but are not limited to,2,2-bis-[3-amino-4-(N-methylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-ethylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-propylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-phenylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-perfluorophenylamino)phenyl]hexafluoropropane,2,2-bis-[3-amino-4-(N-benzylamino)phenyl]hexafluoropropane,2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (generic name:bis(aminophenol)AF), 2,2-bis(3-amino-4-mercaptophenyl)hexafluoropropane,tetraminobenzene, bis-3,4-diaminophenylmethane,bis-3,4-diaminophenylether, and2,2-bis(3,4-diaminophenyl)hexafluoropropane.

The curing agents described above are excellent in mechanical strength,heat resistance, and chemical resistance and give an excellentcrosslinked article having good balance in heat resistance and chemicalresistance.

The amount of the curing agent for the crosslinkable elastomer ispreferably 0.05 to 10 parts by mass, more preferably 1 to 5 parts bymass, relative to 100 parts by mass of the crosslinkable elastomer. Lessthan 0.05 part by mass of the curing agent tends to cause insufficientcrosslinking of the crosslinkable elastomer. More than 10 parts by massof the curing agent tends to cause poor physical properties of thecrosslinked article.

The crosslinkable elastomer composition of the invention may furthercontain an organic base compound.

Examples of the organic base compound include an octadecylaminerepresented by CH₃(CH₂)₁₇—NH₂; an erucamide represented byH₂N—C(O)—(CH₂)₁₁—CH═CH—(CH₂)₇CH₃; an oleamide represented byH₂N—C(O)—(CH₂)₇—CH═CH—(CH₂)₇CH₃; a hexamethylene diamine represented byH₂N—(CH₂)₆—NH₂; and 1,8-diazabicycloundec-7-ene (DBU) represented by

The crosslinkable elastomer composition of the invention and thecrosslinkable elastomer preferably contain a material produced under acondition substantially free from metal compounds. The crosslinkableelastomer composition preferably has a metal content of 100 ppm or less,more preferably 50 ppm or less, still more preferably ppm or less. Acrosslinkable elastomer composition having a quite small metal contentis preferred because such a composition can provide a molded articleusable in semiconductor manufacturing processes and pharmaceuticalprocesses where contamination by metal components should be prevented.The metal content can be measured by frame-less atomic adsorptionanalysis or high frequency inductively coupled plasma atomic emissionspectroscopy. The metal content in the invention refers to the totalmetal content of Fe, Cr, Ni, Cu, Al, Na, Mg, Ca, Zn, Ba, and K. In thecrosslinkable elastomer composition, the total of the amount of thesemetals and the amount of the other metals may fall within the aboverange.

The crosslinkable elastomer composition of the invention can be preparedby mixing each of the above components using a usual elastomerprocessing machine such as an open roll, a Banbury mixer, or a kneader.The composition can also be prepared by a method using an internal mixerand a method of co-coagulating the elastomer from an emulsion mixture.

The method for obtaining a pre-molded article from the above compositioncan be a usual method and can be a known method such as a method ofheat-compressing the composition in a mold, a method of injecting thecomposition into a heated mold, or a method of extruding the compositionwith an extruder. Since extruded products such as a hose and an electricwire can maintain its shape after extrusion, the pre-molded articleextruded without a cross-linking agent can be used as it is. Apre-molded article crosslinked by heating with steam using across-linking agent may also be used. Also, in the case of a moldedarticle, such as an O-ring, that has difficulty in maintaining its shapein an uncrosslinked state after released from the mold, use of apre-molded article that is crosslinked in advance using a cross-linkingagent allows the article to maintain the shape.

In the case of peroxide crosslinking, the crosslinking can be performedunder usual crosslinking conditions of a crosslinkable elastomer. Forexample, a crosslinked article can be obtained by press-crosslinking ofmaintaining the elastomer in a mold under pressure at 120° C. to 200° C.for 1 to 60 minutes and then oven-crosslinking of holding the elastomerin an oven at 120° C. to 250° C. for 0 to 48 hours.

In the case of oxazole crosslinking using a cross-linking agent such asbisaminophenol, the crosslinking can be performed under usualcrosslinking conditions of a crosslinkable elastomer. For example, acrosslinked article can be obtained by press-crosslinking of placing theelastomer in a mold under pressure at 120° C. to 250° C. for 1 to 60minutes and then oven-crosslinking of holding the elastomer in an ovenat 120° C. to 320° C. for 0 to 48 hours. Also, a cross-linking agentsuch as bis(aminophenol)AF may be added to the composition for a knownmethod for crosslinking a crosslinkable elastomer, such as polyaminecross-linking, polyol cross-linking, or peroxide cross-linking, forcombined crosslinking.

Imidazole crosslinking in which a carboxyl group is crosslinked with abisdiaminophenyl cross-linking agent is the most suitable for acarboxyl-containing polymer that has a carboxyl group in an area otherthan the terminals and gives a crosslinked article having favorablephysical properties at a relatively low crosslinking temperature (e.g.,150° C. to 230° C., preferably 170° C. to 200° C.).

The fluoroelastomer molded article of the invention has a weightreduction percentage of 2.5% by mass or less and an amount of particlesgenerated of 0.05% by mass or less after O₂ plasma irradiation under thefollowing conditions, a weight reduction percentage of 1.8% by mass orless and an amount of particles generated of 0.05% by mass or less afterNF₃ plasma irradiation under the following conditions, and a compressionset of 50% or less after aging at 300° C. for 70 hours, the conditionsbeing as follows.

Sample: O-ring (AS-568A-214)

Measurement Details:

(1) O₂ Plasma

Plasma irradiation device: ICP high-density plasma device (MODELRIE-101iPH available from Samco Inc.)

Irradiation Conditions

Gas flow rate: 16 SCCM

RF output: 400 Wh

Pressure: 2.66 Pa

Etching time: 30 minutes

Temperature: 100° C.

These conditions allow a perfluoroelastomer (non-filler) to be etched ata rate of 12000 Å/min.

(2) NF₃ Plasma

Plasma irradiation device: ICP high-density plasma device (MODELRIE-101iPH available from Samco Inc.)

Irradiation Conditions

Gas flow rate: 16 SCCM

RF output: 400 Wh

Pressure: 10 Pa

Etching time: 4 hours

Temperature: 200° C.

These conditions allow a thermally oxidized silicon (SiO₂) wafer film tobe etched at a rate of 90 Å/min.

Such a fluoroelastomer molded article of the invention can be producedfrom the aforementioned crosslinkable elastomer composition of theinvention.

The weight reduction percentage after O₂ plasma irradiation is 2.5% bymass or less, preferably 1.5% by mass or less. The weight reductionpercentage has no particular lower limit because it is preferably assmall as possible. The amount of particles generated after O₂ plasmairradiation is 0.05% by mass or less, preferably 0.03% by mass or less.The amount of particles generated has no particular lower limit becauseit is preferably as small as possible. A weight reduction percentage of2.5% by mass or less enables production of a seal material with betterresistance to O₂ plasma, improving the long-term durability. An amountof particles generated of 0.05% by mass or less reduces attachment ofparticles to a device after O₂ plasma irradiation, preventingcontamination of the device. Furthermore, such an amount of particlesgenerated reduces attachment of particles to a device, reducingimpairment of yield in device production.

The weight reduction percentage after NF₃ plasma irradiation is 1.8% bymass or less, preferably 1.5% by mass or less. The weight reductionpercentage has no particular lower limit because it is preferably assmall as possible. The amount of particles generated after NF₃ plasmairradiation is 0.05% by mass or less, preferably 0.03% by mass or less.The amount of particles generated has no particular lower limit becauseit is preferably as small as possible. A weight reduction percentage of1.8% by mass or less enables production of a seal material with betterresistance to NF₃ plasma, improving the long-term durability. A smallamount of particles generated reduces attachment of particles to adevice after NF₃ plasma irradiation, preventing contamination of thedevice. Furthermore, such an amount of particles generated reducesattachment of particles to a device, reducing impairment of yield indevice production.

The compression set after aging at 300° C. for 70 hours is 50% or less,preferably 45% or less, more preferably 40% or less. A small compressionset enables production of a seal material with better lifetime, whichimproves the long-term durability.

The resistance to O₂ plasma and the resistance to NF₃ plasma can beachieved by using a specific non-oxide ceramic filler. A goodcompression set at high temperature can be achieved by surface-oxidizingthe non-oxide ceramic filler.

Such a molded article can suitably be used as a sealant forsemiconductor manufacturing devices requiring particularly highcleanliness, especially semiconductor manufacturing devices involvinghigh density plasma irradiation. Examples of the sealant includeO-rings, square rings, gaskets, packings, oil seals, bearing seals, andlip seals. The molded article can also be used for a variety of polymerproducts used in semiconductor manufacturing devices, such asdiaphragms, tubes, hoses, a variety of rubber rolls, and belts, and canalso be used for coating materials and lining materials.

The semiconductor manufacturing devices in the invention are not limitedto devices for producing semiconductors, but generally widely includeproducing devices used in the semiconductor field requiring highcleanliness, such as devices for producing liquid crystal panels orplasma panels. Examples thereof include the following.

(1) Etching Systems

dry etching systems, plasma etching systems, reactive ion etchingsystems, reactive ion beam etching systems, sputter etching systems, ionbeam etching systems, wet etching systems, ashing systems

(2) Cleaning Systems

dry etching and cleaning systems, UV/O₃ cleaning systems, ion beamcleaning systems, laser beam cleaning systems, plasma cleaning systems,gas etching and cleaning systems, extraction and cleaning systems,soxhlet extraction and cleaning systems, high-temperature andhigh-pressure extraction and cleaning systems, microwave extraction andcleaning systems, supercritical extraction and cleaning systems

(3) Exposure Systems

steppers, coaters/developers

(4) Polishing Systems

CMP systems

(5) Film Deposition Systems

CVD systems, sputtering systems

(6) Diffusion and Ion Implantation Systems

oxidation and diffusion systems, ion implantation systems

The molded article of the invention exhibits excellent performance as asealant of a CVD system, a plasma etching system, a reactive ion etchingsystem, an ashing system, or an excimer laser exposure system, forexample.

EXAMPLES

The invention is described hereinbelow with reference to, but notlimited to, examples.

Production Example 1 (Heat Treatment)

Silicon carbide (NM-SiC available from Nanomakers, average particlesize: 30 nm) was subjected to a heat treatment in a muffle furnace at800° C. for one hour under an atmospheric condition to provide asurface-oxidized silicon carbide.

<Determination of Surface Oxidation State>

The surface oxidation state of the surface-oxidized non-oxide ceramicwas determined by ESCA using Mg as an X-ray source at 8 kv-10 mA. In thesilicon carbide produced in Production Example 1, 40% of SiC in a 3- to5-nm surface layer was confirmed to be reduced and converted into SiO₂while 60% of SiC was confirmed to remain as SiC (the ratio between thepeak assigned to SiO₂ and the peak assigned to SiC was 2:3).

Examples 1 to 5 and Comparative Examples 1 to 10

According to the mixing compositions shown in Table 1, non-oxide ceramicand a cross-linking agent were added to a fluorine-containing elastomer(TFE/PMVE/CNVE (CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CN)=59.4/40.1/0.5 (mole ratio)),and the components were kneaded with an open roll to prepare acrosslinkable fluoroelastomer composition.

The NphAF used was 2,2-bis[3-amino-4-(N-phenyl amino)phenyl]hexafluoropropane. The heat-treated silicon carbide used was theheat-treated silicon carbide of Production Example 1. The silicon oxideused in Comparative Example 7 was “50” available from Nippon AerosilCo., Ltd., and the surface-treated silicon oxide used in each ofComparative Examples 8 and 9 was RX50 available from Nippon Aerosil Co.,Ltd.

The fluoroelastomer composition obtained in each of Examples 1 and 3 andComparative Examples 1, 3, 6 to 8, and was pressed at 180° C. for 30minutes to be crosslinked, and was then subjected to oven crosslinkingin an oven at 290° C. for 18 hours to provide a 2-mm-thick crosslinkedmolded article and an O-ring (size: AS-568A-214) molded article.Similarly, the fluoroelastomer composition obtained in each of Examples2, 4, and 5 and Comparative Examples 2, 4, 5, and 9 was pressed at 180°C. for 30 minutes to be crosslinked, and was then subjected to ovencrosslinking in an oven at 200° C. to 290° C. for 18 hours to provide a2-mm-thick crosslinked molded article and an 0-ring (size: AS-568A-214)molded article.

The resulting molded articles were measured for the hardness, thecompression set, and the weight reduction percentage and amount ofparticles generated after plasma irradiation by the following methods.Table 1 shows the results.

<Hardness>

The hardness was measured in conformity with JIS K 6301.

<Compression Set>

An O-ring (AS-568A-214) was formed. The compression set of the O-ringwas measured after aging at 300° C. for 70 hours and after aging at 300°C. for 168 hours in conformity with JIS K6262.

<Plasma Resistance>

An O-ring (size: P-24) molded article was prepared and subjected to aplasma irradiation treatment under the following conditions and theweight change before and after the irradiation was determined.

(1) O₂ Plasma

Plasma irradiation device: ICP high-density plasma device (MODELRIE-101iPH available from Samco Inc.)

Irradiation Conditions

Gas flow rate: 16 SCCM

RF output: 400 Wh

Pressure: 2.66 Pa

Etching time: 30 minutes

Temperature: 100° C.

These conditions allowing a perfluoroelastomer (non-filler) to be etchedat a rate of 12000 Å/min

(2) NF₃ Plasma

Plasma irradiation device: ICP high-density plasma device (MODELRIE-101iPH available from Samco Inc.)

Irradiation Conditions

Gas flow rate: 16 SCCM

RF output: 400 Wh

Pressure: 10 Pa

Etching time: 4 hours

Temperature: 200° C.

These conditions allowing a thermally oxidized silicon (SiO₂) wafer filmto be etched at a rate of 90 Å/min.

Each sample was weighed to three decimal places with an electronicanalytical balance and the obtained value was rounded off to two decimalplaces. Three samples were used for each kind, and the average weightreduction percentage of each kind was calculated.

A film was pressed on to the O-ring after plasma irradiation, andwhether generated particles were transferred to the film was visuallyobserved.

TABLE 1 Comparative Comparative Comparative Example 1 Example 2 Example3 Example 4 Example 5 Example 1 Example 2 Example 3 Crosslinkableelastomer (part by mass) TFE/PMVE/CNVE 100 100 100 100 100 100 100 100Filler (part by mass) (average particle size) Oxidized silicon 10 10 1515 20 10 10 15 carbide (0.03 um) Silicon carbide (0.03 um) Siliconcarbide (0.13 um) Silicon oxide (0.03 um) Surface-treated silicon oxide(0.03 um) Crosslinking agent (part by mass) NphAF 0.9 — 0.9 — — 0.9 —0.9 Silicon nitride (0.03 um) — 0.4 — 0.4 0.4 — 0.4 — Hardness (ShoreA)72 71 75 75 80 72 71 75 Compression set 33 33 42 36 47 43 59 55 (70hr/300° C.) (%) Compression set 58 46 75 (168 hr/300° C.) (%) Plasmaresistance O₂ plasma irradiation Weight reduction 1.90 1.89 1.42 1.400.98 1.92 1.93 1.51 percentage (%) Surface particle 0.01 0.01 0.01 0.010.01 0.01 0.01 0.01 amount (%) Particle transferring Absent AbsentAbsent Absent Absent Absent Absent Absent NF₃ plasma irradiation Weightreduction 1.79 1.78 1.34 1.43 1.39 1.82 1.78 1.42 percentage (%) Surfaceparticle 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 amount (%) Particletransferring Absent Absent Absent Absent Absent Absent Absent AbsentComparative Comparative Comparative Comparative Comparative ComparativeComparative Example 4 Example 5 Example 6 Example 7 Example 8 Example 9Example 10 Crosslinkable elastomer (part by mass) TFE/PMVE/CNVE 100 100100 100 100 100 100 Filler (part by mass) (average particle size)Oxidized silicon 15 20 15 15 15 15 carbide (0.03 um) Silicon carbide(0.03 um) Silicon carbide (0.13 um) Silicon oxide (0.03 um)Surface-treated silicon oxide (0.03 um) Crosslinking agent (part bymass) NphAF — — 0.9 0.9 0.9 — 0.9 Silicon nitride (0.03 um) 0.4 0.4 — —— 0.4 — Hardness (ShoreA) 75 80 74 74 75 75 60 Compression set 67 84 3870 37 33 34 (70 hr/300° C.) (%) Compression set 83 85 54 46 45 (168hr/300° C.) (%) Plasma resistance O₂ plasma irradiation Weight reduction1.54 1.15 1.71 — 1.40 1.38 3.01 percentage (%) Surface particle 0.020.01 0.07 — 0.02 0.02 0.02 amount (%) Particle transferring AbsentAbsent Present — Absent Absent Absent NF₃ plasma irradiation Weightreduction 1.44 1.39 1.62 — 2.10 2.17 2.73 percentage (%) Surfaceparticle 0.02 0.01 0.07 — 0.01 0.01 0.02 amount (%) Particletransferring Absent Absent Present — Absent Absent Absent

The invention claimed is:
 1. A crosslinkable elastomer compositioncomprising a crosslinkable elastomer and a surface-oxidized non-oxideceramic filler, wherein a peak assigned to an oxide and a peak assignedto a non-oxide give a ratio (oxide:non-oxide) of 3:7 to 6:4 in ESCAmeasurement of surface-oxidized non-oxide ceramic filler, wherein thenon-oxide ceramic filler has an average particle size of 0.1 μm orsmaller.
 2. The crosslinkable elastomer composition according to claim1, wherein the non-oxide ceramic filler is silicon carbide.
 3. Thecrosslinkable elastomer composition according to claim 1, wherein thecrosslinkable elastomer is a copolymer of tetrafluoroethylene andperfluoro(alkyl vinyl ether).
 4. A fluoroelastomer molded articleproduced from the crosslinkable elastomer composition according to claim1, having a weight reduction percentage of 2.5% by mass or less and anamount of particles generated of 0.05% by mass or less after 02 plasmairradiation under predetermined conditions, a weight reductionpercentage of 1.8% by mass or less and an amount of particles generatedof 0.05% by mass or less after NF₃ plasma irradiation under thepredetermined conditions, and a compression set of 50% or less afteraging at 300° C. for 70 hours, wherein the predetermined conditions are:sample: O-ring (AS-568A-214), measurement details: (1) O₂ plasma plasmairradiation device: ICP high-density plasma device, irradiationconditions, gas flow rate: 16 SCCM, RF output: 400 Wh pressure: 2.66 Pa,etching time: 30 minutes, temperature: 100° C., these conditionsallowing a perfluoroelastomer (non-filler) to be etched at a rate of12000 Å/min, (2) NF₃ plasma plasma irradiation device: ICP high-densityplasma device, irradiation conditions, gas flow rate: 16 SCCM, RFoutput: 400 Wh, pressure: 10 Pa, etching time: 4 hours, temperature:200° C., and these conditions allowing a thermally oxidized silicon(SiO₂) wafer film to be etched at a rate of 90 Å/min.